// 代码索引 3-2-2-1
#include <iostream>
#include <Eigen/Dense>

int main()
{
    Eigen::Matrix2d a;
    a << 1, 2,
         3, 4;
    Eigen::Vector3d v(1,2,3);
    std::cout << "a * 2.5 =\n" << a * 2.5 << std::endl;
    std::cout << "0.1 * v =\n" << 0.1 * v << std::endl;
    std::cout << "Doing v *= 2;" << std::endl;
    v *= 2;
    std::cout << "Now v =\n" << v << std::endl;
}